STRATIFICATION 261 
Cause of Stratification. — Minor variations. These 
strata and laminz represent differences in the con- 
ditions of accumulation. There are many ways in 
which such differences may be caused. For instance, 
in the delta of the 
Mississippi, there is 
a gradual and rather 
rapid accumulation 
of fine-grained sedi- 
ment, brought down 
by the river. Ordi- 
narily itis a brownish 
mud, but when its 
tributary, the Red 
River of Arkansas, 
is in flood, the color of 
the muddy water is 
changed from brown 
to red; and during 
this time the sedi- 
ment that is depos- 
ited upon the delta is 
Beds of stratified rock. Hard sandy layer in 
foreground is seen projecting from left side 
of gorge. 
of reddish hue. So, according to the condition of the 
flood, there are deposited alternate layers of red or brown 
colored sediment, which in other respects are alike. 
On many coasts where rivers are emptying their 
waters, the sediment they bring is ordinarily muddy; 
